Generally, in a waterbed structure, a water inlet and an exhaust port are needed to vent air as the given waterbed's water compartment is filled with water. While the water is being filled, the exhaust port is opened so that air within the water compartment of the waterbed may vent out. If air remains within the water compartment of the waterbed, a disturbingly loud sound of water flowing within the water compartment may be emitted to a user lying on the waterbed. Also, with extended use, air may gradually collect within the compartment. If this air is not effectively vented out, the waterbed will lack softness and elasticity.
Generally, the structure of exhaust ports known in the prior art are such that the air in the water compartment will not be adequately released. Often, in releasing the air, water is also released. Prior art exhaust ports are typically formed simply with a hole for access to the water compartment and a plug cover therefor. The plug cover is opened during venting, and since water within the waterbed is under an inner pressure, it will tend to flow out, potentially wetting the waterbed's outer surface. The water will also tend to block the release of air retained within the water compartment until it is removed by flow out of the compartment. This is a drawback that must be overcome.
In U.S. patent application Ser. No. 08/877,183, filed by the inventor of the present invention, a floating ball is installed within the exhaust port, and a lattice cover for covering a through hole prevents the floating ball from being released. Thus, only water and air are permitted to flow through the hole. A space having an upper portion of conic shape is formed between the cover and the exhaust port to receive the floating ball. The venting of air is then controlled by exploiting both the buoyancy and the weight of the floating ball. When the water flows to the exhaust port, the floating ball rises to rest against the outlet of the conic space so that water is prevented from flowing out. When air is released to the exhaust port, the water level declines, causing the floating ball to descend. The conic portion which had been blocked by the ball is thereby opened to allow the air to vent out. This structure, however, does not sufficiently prevent the flow of water out the exhaust port. A need, therefore, exists for a more effective venting valve assembly.